Quote - There are bugs in earlier versions of Poser 7 that appear as artifacts at bucket boundaries, if and only if you are running light-based AO, and at certain specific settings. If you are using an old, buggy, release of Poser 7, then you may see a change in the artifacts. Thus it is possible to "see" a change in something when changing bucket size. But this is only in the broken versions. This is not worth explaining, really. If you're not at SR3, get there.

Also, displacement isn't calculated very far from the bucket boundary (or possibly not at all), so if you have an item with a lot of displacement (as is used for fur sometimes) near a bucket boundary then it can get cut off.